Heavy duty electrical plug

ABSTRACT

Heavy-duty electrical plug having a tubular elastomeric body portion, a disc tightly seated in one end thereof, a plurality of male thermal contacts mounted in the disc, a substantially rigid ring fixed tightly about said end of the body portion, a threaded nipple mounted in the other end of the body portion, a tapered elastomer grommet seated in the nipple, and a cord grip nut threaded on the nipple.

United States Patent David E. Kramer Northbrook, 111.

Dec. 15, 1969 Nov. 2, 1 971 Daniel Woodhead Company Northbrook, Ill.

Inventor Appl. No. Filed Patented Assignee HEAVY DUTY ELECTRICAL PLUG 3 Claims, 4 Drawing Figs.

ILLS. C1 339/63 M, 339/196 M, 24/21] R Int. C1 H01r 15/06, l-lOlr 33/06 Field of Search 339/14 R,

14 P, 59,60, 62, 63, 95 R, 95 A, 94,176 R, 176 L, 176 M, 176 8,195,196, 206209; 285/242, 255; 24/211 R, 230 SL, 260; 215/95 [56] References Cited UNITED STATES PATENTS 2,061,190 11/1936 Ericson 339/63 2,125,555 8/1938 Frantz 339/63 Primary Examiner-Marvin A. Champion Assistant Examiner-Lawrence J. Staab Attorney-Johnston, Root, OKeefe, Keil, Thompson &

Shurtleff HEAVY DUTY ELECTRICAL PLUG INTRODUCTION The invention herein concerns improvements in heavy-duty electrical plugs especially adapted for hospital use. There is an increasing awareness in the hospital field of the need for safe electrical patient-treating and patient-care apparatus. Even very minor voltage leakages in electrical or electronic patienttreating instruments may be critical to the effectiveness of the treatment or the instrument readings. Furthermore with the increased use of electrically operated patient beds and similarly powered other patient-care units, considerable concern is directed toward the safeguarding against shockproducing voltage leakage which could be transmitted to the patient or hospital personnel.

One of the major areas of concern lies in electrical plugs for wall or like electrical outlet receptacles. There is a rising demand for well insulated, damage resistant and substantially tamper-proof electrical plugs.

THE INVENTION HEREIN The invention herein has for its primary objectives the provision of improvements in the structure of heavy-duty electrical plugs having appropriate safeguards in terms of electrical insulation, damage resistance to the terminal-containing hollow body portion and projecting male terminal contacts, and tamper-proof qualities. These improvements are provided by heavy duty electrical plugs embodying nonconducting body portions and parts interfitted or coupled therewith, said parts including a nonconductive, substantially rigid disc of moldable synthetic resin or polymer with the male terminal contacts rigidly molded into and projecting from the disc. It has been found by experience that the seating of this disc in tightly fitted relationship in one end of a tubular elastomeric body portion of the plug can be substantially improved in terms of the damage resistance and tamper-proof qualities in this portion of the plug by fitting over this end of the body portion a substantially rigid ring. This ring adds rigidity to the assembly of the disc and the end of the body portion whereby the electrical plug as a whole is considerably more damage resistant in the area of the disc and body portion assembly and also in the area of the male terminal contacts when the plug is accidentally struck or pushed laterally.

The substantially rigid ring is preferably made of a nonconducting material such as a moldable thermoplastic resin or polymer. The cylindrical inner face of the ring preferably has one or more projections thereon which will bite into the elastomeric material of the body portion in a fashion to resist displacement of the ring off of the end of the body portion. Such projections preferably take the form of one of more peripheral circular ribs or ridges, but other means such as knurling or other roughening of the inner face of the ring may be used.

THE DRAWINGS A preferred embodiment of the invention is illustrated in the drawings wherein:

FIG. 1 is a perspective view of the electrical plug assembly;

FIG. 2 is a perspective view of the electrical plug with the ring separated therefrom;

FIG. 3 is an exploded, perspective view showing the individual components ofthe plug; and

FIG. 4 is a fragmentary view of the male terminal end of the tubular body portion with the ring separated therefrom and shown in diametric cross section.

THE ILLUSTRATED EMBODIMENT The heavy-duty electrical plug has the usual male terminal contacts 11 and 12 and a male ground contact 13. These contacts may be made in any desired dimensions, spacings and/or relative positions. The contacts 11-13 are rigidly mounted in a disc plate 14 which is preferably made of a moldable thermoplastic resin or polymer into which the contacts may be pressed or integrally molded in tight fitting relationship.

The rear face of the disc plate 14 has molded integrally therewith three divider walls 15, 16 and 17 extending in equiangular spacing from the radial center of the rear face. These divider walls serve as insulating separators for the three terminals to which the power and ground wires are connected inside the tubular elastomeric body portion 22 of the plug. The three terminals respectively comprise a screw 13 threaded in a metal plate 19, the latter being an integral part of the respective male contacts 11-13.

The tubular body portion 22 is a tubular molding of an elastomeric material, i.e., a natural or synthetic rubber. Its disc plate-containing end 21 defines a hollow cylinder of elastomeric material which may be of the same dimension as the remaining part of the tubular body portion 22, but preferably is a smaller outside diameter to make the ring 33, hereinafter described, lie substantially flush with the remainder of the body portion 22.

The opposite end of the body portion 22 has a ring 23 bearing a projecting male-threaded nipple 24 cemented or otherwise tightly secured in that end. The ring 23 and nipple 24 preferably are composed of an integrally molded ther' moplastic synthetic polymer or resin.

A tapered, elastomeric grommet 25 fits in and seats in the nipple 24. It has a beveled outer edge 26 and a wire-accommodating longitudinal passage 27. A frustoconical friction ring 28 rests upon the beveled edge 26 and presses thereagainst when the annular shoulder 31 of the cord grip nut, bearing female threads 30, is threaded tightly on the nipple 24. In this arrangement the electrical cord 32 may be tightly gripped by the walls of the passage 27 by virtue of elastomeric deformation via the ring 28 from the tightly threaded cord grip nut 29. The diameter of the cord 32 is approximately the same diameter as that of the passage 27.

The disc plate-containing end 21 of the tubular body portion 22 has pressed thereover a substantially rigid ring 33 again preferably a molding of synthetic resin or polymer. The inner face 40 of the ring 33 has substantially the same diameter as the diameter of the end 21 whereby the end 21 and ring 33 are in tight frictional engagement. The body portion-facing end 34 of the ring has a smaller inner diameter than the remaining inner diameter of the ring to provide a lip or rib or shoulder 35 adapted to bite into the outer face of the elastomeric end 21 of the body portion 22. Preferably such biting occurs to a greater degree during attempted removal of the ring 33 from the end 21 than occurs during pressing of the ring onto the body portion. In the illustrated instance, this is attained by the shoulder formed between the segments of the inner face 40 of different diameters so that it faces away from the body portion 21 as the ring is being placed upon the body portion 21.

In addition to the ring 33, the assembly of the end 21 of the tubular body 22 and the disc plate 14 may be strengthened against displacement of the disc plate from the end 21 by providing three axial grooves 36 in the periphery of the disc plate 14. These grooves mate with three ribs 37 on the inner face of the end 21. Additionally the plate 14 may have a peripheral flange or rib 33 which matingly seats in the peripheral undercut 39 in the inner face of the end 21.

The heavy-duty plug 10 is assembled by inserting the cord 33 through the nut 29, the friction ring 28, the grommet 25 and the body portion 22. The projecting end of the cord, after appropriate stripping of the wires, is attached to the respective terminals l3, 19. The cord is then pulled back until the disc plate 14 rests on the end 21 of the body portion. If the peripheral edge of the disc plate 14 contains recesses 36 adapted to align with ribs 37 on the inner face of the end 21, the latter are aligned and the disc is pressed into the end 21 until the projecting annular rib or flange 33 is seated in an annular groove or undercut 39. Thereafter the nut 29 is threaded tightly onto the nipple 24, and the ring 33 is pressed onto the end 21 of the body portion 22 to provide an assembly as shown in FIG. 1.

It is thought that the invention and its numerous attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope of the invention, or sacrificing any of its attendant advantages, the forms herein disclosed being preferred embodiments for the purpose of illustrating the invention.

In the claims:

1. A heavy-duty electrical plug comprising a tubular elastomeric body portion, a disc tightly fitted in one end of said body portion, a plurality of male terminal contacts mounted in and projecting from said disc, and a cylindrical, substantially rigid ring press-fitted tightly about said end of said body portion to addrigidity to the assembly of said disc and said end of said body portion, the inner face of said ring having cylindrical inner face segments of different diameters with an annular shoulder therebetween, and said shoulder facing toward said one end of said body portion whereby said ring may be pressed over said end of said body portion and said annular shoulder bites into the elastomer of said end of the body portion to resist removal of said ring from said end.

2. A heavy-duty electrical plug as claimed in claim 1 wherein said disc comprises a plastic plate with said contacts mounted rigidly therein and projecting from the front face thereof, and wire-receiving contacts on the rear face of said disc.

3. A heavy-duty electrical plug comprising a tubular elastomeric body portion, a disc tightly fitted in one end of said body portion, a plurality of male terminal contacts mounted in and projecting from said disc, and a cylindrical, substantially rigid ring press-fitted tightly about said end of said body portion to add rigidity to the assembly of said discs and said end of said body portion, the inner face of said ring having cylindrical inner face segments of different diameter with an annular shoulder therebetween, and said shoulder facing toward said one end of said body portion whereby said ring may be pressed over said end of said body portion and said annular shoulder bites into the elastomer of said end of the body portion to resist removal of said ring from said end, said disc comprising a plastic plate with said contacts mounted rigidly in and projecting from the front face thereof, wire-receiving contacts on the rear face of said discs, a plurality of circumferentially spaced, axial grooves in the periphery of said disc, and a plurality of circumferentially spaced, axial, elastomer ribs on the inner face of said end of said body portion matingly fitted in said grooves to strengthen the assembly against displacement of said disc from said end of said body portion.

l =8 II t i UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5, 7,9 1 Dated November 2, 1971 Inventor-(g) David E. Kramer It is certified that errer appears in the above-identified patent and that; said Letters Patent are hereby corrected as shown below:

, "I Celumn 4, line 10, claim 3, "discs" should read disc line l2, claim 3, "diameter" should read diameters Signed and sealed this 11th day" of April 1972.

A'ttest;

EDL'JABL'J MJFLEIGIIBIQJR. ROBERT T CHA K Attestingg Officer Commissioner of Patents 

1. A heavy-duty electrical plug comprising a tubular elastomeric body portion, a disc tightly fitted in one end of said body portion, a plurality of male terminal contacts mounted in and projecting from said disc, and a cylindrical, substantially rigid ring press-fitted tightly about said end of said body portion to add rigidity to the assembly of said disc and said end of said body portion, the inner face of said ring having cylindrical inner face segments of different diameters with an annular shoulder therebetween, and said shoulder facing toward said one end of said body portion whereby said ring may be pressed over said end of said body portion and said annular shoulder bites into the elastomer of said end of the body portion to resist removal of said ring from said end.
 2. A heavy-duty electrical plug as claimed in claim 1 wherein said disc comprises a plastic plate with said contacts mounted rigidly therein and projecting from the front face thereof, and wire-receiving contacts on the rear face of said disc.
 3. A heavy-duty electrical plug comprising a tubular elastomeric body portion, a disc tightly fitted in one end of said body portion, a plurality of male terminal contacts mounted in and projecting from said disc, and a cylindrical, substantially rigid ring press-fitted tightly about said end of said body portion to add rigidity to the assembly of said discs and said end of said body portion, the inner face of said ring having cylindrical inner face segments of different diameter with an annular shoulder therebetween, and said shoulder facing toward said one end of said body portion whereby said ring may be pressed over said end of said body portion and said annular shoulder bites into the elastomer of said end of the body portion to resist removal of said ring from said end, said disc comprising a plastic plate with said contacts mounted rigidly in and projecting from the front face thereof, wire-receiving contacts on the rear face of said discs, a plurality of circumferentially spaced, axial grooves in the periphery of said disc, and a plurality of circumferentially spaced, axial, elastomer ribs on the inner face of said end of said body portion matingly fitted in said grooves to strengthen the assembly against displacement of said disc from said end of said body portion. 